See the screenshots attached above. It was not easy to catch the first one (VirtualBox BIOS)... on the 2nd. Screenshot I previously had a working OSX-Boot progress. It was working on a previous version of VirtualBox (Sorry, cannot say which one I had before the upgrade).

I can agree that Version 4.2.1 seems to have fixed the errors thrown in the screenshots that have been attached.

BUT the OSX Guest-Machine (using EFI-Mode) still doesn't boot properly. It runs into something like a kernel error.

To be shure there is no configuration mistake (since the upgrade to 4.2.x) I've downgraded VirtualBox back to latest 4.1.22 (r80657) and voila - the OSX Guest worked again without any change to the VBox configuration!

So there still must be any other error that blocks booting of OSX/EFI Guests on 4.2.x.

Is there anybody who can confirm/disconfirm that?
If there is anybody able to run OSX Guests using EFI please let us know how.

So please re-open these bugtrack...

BTW: I also tried the EFI-Hacks for X86 Machines using a tiny Bootloader-ISO that should help PC's running (Intel-based) OSX-Guests without EFI (also known as "Hackintosh" Loaders). But none of these tools worked yet for me (tested on real PC and VirtualBox).